| 摘要 |
A method and arrangement for controlling an AC motor which exhibits a constant torque characteristic at a rotational speed N below a base speed Nb and a constant output characteristic at a rotational speed N above the base speed Nb, the method (which is utilised by the arrangement) comprising the steps of finding a base speed N@ after limiting the output power of the AC motor, N @ being derived from the base speed Nb and the ratio eta between maximum output power Pmax1 and maximum output power Pmax2 before and after the output power of the AC motor is limited, respectively, rendering the slip frequency of the AC motor constant until the rotational speed N of the AC motor reaches the base speed N@, varying the slip frequency in inverse proportion to the rotational speed N for N between N@ and Nb (N</=N</=Nb) and varying the slip frequency in proportion to the rotational speed N for N above Nb (Nb < N), whereby the output power of the AC motor is rendered constant at a rotational speed N above N@. |
